Permanent magnet materials currently in use include alnico, hard ferrite and rare earth element-cobalt magnets. Recently, new magnetic materials have been introduced containing iron, various rare earth elements and boron. Such magnets have been prepared from melt quenched ribbons and also by the powder metallurgy technique of compacting and sintering, which was previously employed to produce samarium cobalt magnets.
Suggestions in the prior art for rare earth element permanent magnets and processes for producing the same include: U.S. Pat. No. 4,597,938. Matsuura et al. which discloses a process for producing permanent magnet materials of the Fe-B-R type by: preparing a metallic powder having a mean particle size of 0.3-80 microns and a composition consisting essentially of, in atomic percent, 8-30% R representing at least one of the rare earth elements inclusive of Y, 2 to 28% B and the balance Fe; compacting and sintering the resultant body at a temperature of 900.degree.-1200.degree. C. in a reducing or non-oxidizing atmosphere. Co up to 50 atomic percent may be present. Additional elements M (Ti, Ni, Bi, V, Bb, Ta, Cr, Mo, W, Mn, Al, Sb, Ge, Sn, Zr, Hf) may be present. The process is applicable for anisotropic an isotropic magnet materials. Additionally, U.S. Pat. No. 4,684,406, Matsuura et al., discloses a certain sintered permanent magnet material of the Fe-B-R type, which is prepared by the aforesaid process.
Also, U.S. Pat. No. 4,601,875, Yamamoto et al. teaches permanent magnet materials of the Fe-B-R type produced by: preparing a metallic powder having a mean particle size of 0.3-80 microns and a composition of, in atomic percent, 8-30% R representing at least one of the rare earth elements inclusive of Y, 2-28% B and the balance Fe; compacting: sintering at a temperature of 900.degree.-1200.degree. C.; and, thereafter, subjecting the sintered bodies to heat treatment at a temperature lying between the sintering temperature and 350.degree. C. Co and additional elements M (Ti, Ni, Bi, V, Nb, Ta, Cr, Mo, W, Mn, Al, Sb, Ge, Sn, Zr, Hf) may be present. Furthermore, U.S. Pat. No. 4,802,931, Croat, discloses an alloy with hard magnetic properties having the basic formula RE.sub.1-x (TM.sub.1-y B.sub.y).sub.x. In this formula, RE represents one or more rare earth elements including scandium and yttrium in Group IIIA of the periodic table and the elements from atomic number 57 (lanthanum) through 71 (lutetium). TM in this formula represents a transition metal taken from the group consisting of iron or iron mixed with cobalt, or iron and small amounts of other metals such as nickel, chromium or manganese.
Another example of a rare earth element-iron-boron and rare earth element-iron-boron hydride magnetic materials is presented in U.S. Pat. No. 4,663,066 to Fruchart et al. The Fruchart et al. patent teaches a new hydrogen containing alloy which contains H in an amount ranging from 0.1-5 atomic percent. The alloy of Fruchart et al. is prepared by a process wherein the rare earth element-iron-boron compound at room temperature is hydrogenated under a hydrogen pressure above 10 bar (10.times.10.sup.5 Pa) and below 500 bar (500.times.10.sup.5 Pa). Following the hydrogenation process, the compound is subjected to a dehydrogenation cycle by subjecting it to temperatures ranging from 150.degree. C. to 600.degree. C., whereby all of the hydrogen is removed.
Still another example of a rare earth element-iron-boron magnetic material is presented in U.S. Pat. No. 4,588,439 to Narasimhan et al., which describes a permanent magnet material of rare earth element-iron-boron composition along with 6,000-35,000 ppm oxygen.
However, prior art attempts to manufacture permanent magnets containing rare earth element-iron-boron compositions utilizing powder metallurgy technology have suffered from substantial shortcomings. In particular, these inventions teach that the rare earth element-iron-boron magnetic material has a very high selectivity to hydrogen. As a result, in commercial applications, hydrogen which is present in a normally humid atmosphere is easily absorbed by the magnet alloy and causes the disintegration thereof.